The present invention relates to security devices, and more particularly to motion sensing apparatus for use in a perimeter intrusion detection system.
It is quite common to employ a wire fence as a barrier surrounding an area to be protected. Various devices have been employed to provide a warning if any attempt is made to interfere with the protective function of the fence. A number of these intrusion detection systems, particularly those protecting large-scale high security facilities, typically provide a combination of a physical barrier and an electronic detection capability. Often times, sensing devices of the type described herein are used to detect persons who attempt to cut, climb, lift, or contact the fence. Vibration sensors are one type of such devices. In a typical implementation, at least one vibration sensor is mounted on a fence section such as a chain link fence segment. When an intruder contacts the chain link fence, the vibrations are transmitted to the sensor and detected. A control station receives the vibration indication and generates a corresponding alarm condition.
However, these prior art vibration sensing systems suffer from a number of disadvantages. Primary among these is the extreme difficulty of properly aligning the vibration sensor when mounting on the fence. Improper alignment of the sensor can greatly affect its sensitivity, causing it to detect vibration in response to either too little or too great of a force. Additionally, prior art constructions lacked the ability to set the direction of sensitivity for the sensor, which may be required for objects tending to naturally move along one direction, such as fences.
Therefore, in accordance with the present invention, a vibration sensor includes a housing and a directional actuator. The actuator includes two pairs of conductive arcs as part of an actuator assembly. Each pair of arcs includes one smooth and one irregularly shaped arc. Two movable conductive spherical elements normally rest in contact with each pair of arcs, respectively, and thus produce an electrical interconnection therebetween. In operation, in response to the application of predetermined force to the actuator, the two movable conductive spherical elements break contact with at least one of the arcs, thus opening the respective electrical connections. Each pair of conductive arcs is coupled to a logic circuitry processing unit for sensing the interruption in the electrical interconnection and determining in response thereto whether an alarm condition should be reported.
The actuator assembly is located inside an actuator cover, which is divided into two atmospheres, each containing a pair of conductive arcs and a movable conductive spherical element. The actuator cover is placed inside an ellipse-shaped sensor cover made up of two halves. A coupling ring of the cover is inserted into a mounting means, which is attached to a fence. A plurality of such sensors are connected by an electrical cable and placed on a wire fence at spaced intervals between each divided section of the fence. The system therefore protects against attempts of persons to climb, lift, or cut the fence itself.
In one embodiment, the invention provides a vibration sensor employed for detecting movement of a physical barrier that includes a sensor cover and an actuator assembly. The sensor cover includes a coupling portion for coupling the sensor to a physical barrier at a first orientation. The sensor cover is also adapted to secure an actuator assembly in at least one predetermined orientation relative to the level horizontal when the sensor is coupled to the physical barrier at said first orientation. The actuator assembly includes a first pair of conductive arcs and a second pair of conductive arcs, where each pair of conductive arcs is coupled as a corresponding ends of a switch to a control circuit. The first pair of conductive arcs is positioned substantially parallel to the second pair of conductive arcs. The actuator assembly also includes a first conductive sphere and a second conductive sphere. The first sphere rests between and engages each arc from the first pair of conductive arcs to provide an electrical connection between the first pair of conductive arcs while the second sphere rests between and engages each arc from said second pair of conductive arcs to provide an electrical connection between the second pair of conductive arcs. The sensor also includes a control circuit coupled to at least each arc of the first pair of conducive arcs and the second pair of conductive arcs. The control circuit indicates an alarm to a sensor output in response to a break in the electrical connection between arcs of a pair of conductive arcs.
In another embodiment, the invention provides a method for installing a sensor on a physical barrier, the sensor including an actuator assembly adapted to sense vibrational disturbances to the sensor, where the actuator assembly is associated with varying sensitivity to vibrations based on the angular orientation of the actuator assembly relative to the level horizontal. The method includes securing the actuator assembly at an angular orientation relative to a sensor body by employing a securing pin. This securing pin is coupled at a first end to a pivoting anchor and is coupled at a second end to the exterior surface of the sensor body within a channel opening, which allows for displacement of said securing pin second end along said channel. The method also includes rigidly coupling the sensor to the physical barrier. Finally, the method includes adjusting the angular, internal, position of the actuator by adjusting the position of the second end of the securing pin to set the sensitivity of the sensor.